import java.util.Scanner;

public class demo3 {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        int n=scanner.nextInt();
        int temp=26;
        int x=n;
        int k=0;

        while (x>0){
            x/=temp;
            temp*=temp;
            k++;
        }
        int ret=26;
        for (int i = 1; i <k ; i++) {
            ret*=ret;
        }
        StringBuilder stringBuilder=new StringBuilder();
        while (--k>0){
            stringBuilder.append("Z");
        }
        int zim=n%ret;//记录剩余值
        stringBuilder.append(zim+'A');
        System.out.println(stringBuilder.toString());

    }
}
